ROAD SURFACE STRUCTURE MONITORING AND ANALYSIS USING HIGH PRECISION GPS MOBILE MEASUREMENT SYSTEMS (MMS)

Transcription

1 ROAD SURFACE STRUCTURE MONITORING AND ANALYSIS USING HIGH PRECISION GPS MOBILE MEASUREMENT SYSTEMS (MMS) Bonifacio R. Prieto PASCO Philippines Corporation, Pasig City, 1605, Philippines KEY WORDS: Mobile Mapping System, Road Crack Analysis, Road Condition management, IRI ABSTRACT: Roads are the lifeline of a nation. This paper aims to introduce an effective road maintenance program using enhanced automated data capturing systems that simplifies evaluation of deteriorating pavement surface, resulting to an efficient management and maintenance of road infrastructure assets. PASCO Philippines had carried out numerous Road Pavement Surface Deterioration Survey using data captured from High Precision GPS Mobile Measurement System (MMS) vehicles. These MMS vehicles can capture point cloud data and high resolution images while the vehicle is in motion. The acquired high quality data can then be used for analysis and evaluation of road surface condition based on the International Roughness Index (IRI). MMS can calculate the position of the vehicle every 0.5 seconds using GPS and collects the 3 axis orientation using Inertial Measurement Unit (IMU) sensors to determine the vehicle's supplementary position. Several precision calibrated sensors such as 3 GPS units in triangle position, IMU and odometer (distance and acceleration), and 6 high definition cameras working in tandem with 4 long range/high density laser scanner (within 10cm(rms)@ 7m precision), allows the vehicle to implement overlaying of colored 3D laser point cloud data and image data. The resulting data can be used to grasp precise road spatial information. A 3D Mapping system (PADMS), developed by PASCO Corp. Japan, can superimpose the acquired 3D laser point clouds onto the high resolution images taken by the cameras. Users can directly edit Geographic Information Systems (GIS) data, such as shape files and geographic database, generate cross sectional views of terrain and features at any position to obtain height data. Rutting (wheel track), longitudinal roughness or evenness can be automatically extracted, to some extent, through 3D point cloud data analysis. Since it is difficult to acquire road cracks in point cloud data, it can be extracted by highly qualified operators utilizing the captured high resolution images. Road flatness characteristics (σ) is corrected using supplementary values acquired from other information. IRI of each segment or section is calculated using the formula IRI 1.33σ INTRODUCTION Roads are the lifeline of a nation. The pace of development of a country depends upon the production of goods and services as well as their movement over space. Therefore, an efficient means of transport are pre-requisites for fast development. In order to achieve that, an effective road maintenance program is required. Mobile mapping technology has been researched and developed since late 1980s. The integration of the various sensors involved, such as GPS, INS, laser scanners, CCD cameras and others, in a mapping system has been investigated and demonstrated by Hein(1989), Krabill(1989), Schwarz et al.(1993b) and others. During the last 5 years the technology has become more practical and affordable, mainly, because of advancement in remote sensing technology. PASCO Philippines, in coordination with PASCO group of companies, had carried out numerous Road Pavement Surface Deterioration Survey using data captured from high-accuracy GPS Mobile Measuring Equipment (MMS). MMS is a vehicle mounted, laser surveying device, for acquisition and measurement of 3D coordinate data, and data capture of sequence of images and its surroundings. PASCO utilizes these vehicles for sophisticated and efficient road maintenance and management work. Data collected from these vehicles are being used for different survey and mapping applications, such as; Topographical Surveying Map Creation Facility/Road Management Road Condition Maintenance and management work 2. MMS FEATURES AND CAPABILITY 2.1 High Accuracy three-dimensional (3D) measurement MMS vehicles can capture point cloud data and high resolution images while the vehicle is in motion with an absolute accuracy within 10cm, and a relative accuracy within 1cm. Three GPS antennas in triangular configuration, and laser

2 scanners mounted on the vehicle s roof, capture vehicle position precisely. The device computes the position/location and posture to a high degree of accuracy using data collected from GPS (three units), Inertial Measurement Unit (IMU) and Odometer. GPS correction is carried out through FKP format (surface correction parameters), the IMU captures angle and acceleration, while the odometer system captures and adjusts travel distance. In locations where GPS measurements may be blocked, such as tunnels, the vehicle can calculate its supplementary position by interpolating data collected from the Inertial Measurement Unit (IMU) sensors and in-wheel odometer. Figure 1: MMS Sensor placement configuration 2.2 Wide-angle Camera Images and High-density Laser Point Clouds The system is able to output two types of data. One is 3D point cloud from 4 long range/high density laser scanner (within 10cm (rms)@ 7m precision). Another is high resolution digital image. A total of 6 high definition cameras mounted at 80 degrees horizontally and 64 degrees vertically, allows for a 360 degrees viewing angle of the entire periphery. The MMS can take accurate values of self-position and attitude, so each type of data has correct coordinates of X-Y-Z. This means that, accurate measurement of the road surface and roadside is possible, and, it allows the vehicle to implement overlaying the image data onto the captured laser point cloud. The data (combination of 3D laser point and camera images), as shown in Figure 3, presents a 3D visual scenery of the driven route that is spatially correct and can be used to determine location, length, width and other spatial related information from roads and other road related facilities. Taking advantage also of the high resolution camera, the condition of the road surface can be marked and analyzed for surface deterioration such as road cracks, potholes, rutting and other signs of deteriorating properties. Figure 2: Position and Perspective view of the 6 mounted cameras (Photo courtesy of Mitsubishi Electric Corp.)

3 (a) 3D point cloud model (b) Image model Figure 3: High density laser point cloud can be captured in one pass and can be displayed in color by superimposing the image from the camera. (c) Point Cloud Overlay 3. PHOTOGRAMMETRY AND DIGITAL MAPPING SOFTWARE (PADMS) PASCO Corp. of Japan, have developed a software that can directly utilize the output of these MMS vehicles for various Mapping purposes. PADMS-Solid 3D, can superimpose the acquired colored laser point data with the images recorded by the cameras, thereby creating a 3D image. All MMS acquired data can be displayed in a multi windowed user interface. Using this software, users can have access to the following; 3D View ( main window where all data input and acquisition mainly occur) 2D View ( A secondary view consisting mostly of colored point cloud) Cross Section View Vertical Section View Horizontal Section View Camera Views (all 6) MMS course data (with course length and course playback) Panoramic View (180 degrees) Figure 4: PADMS User interface showing the different views

4 With integration to GIS and CAD based software, such as ARCGIS and AutoCAD, acquisition of data to common vector data formats, ie shape files (.shp) and drawing Files (.dwg) is easy and requires less workflow process Feature Plotting One of the main strength of PADMS is in topographical survey. Planimetric maps of roads can be accurately created by direct tracing of topographic features in the acquired image. Colored cloud points can serve as reference to ensure that correct spatial information are acquired. Using MMS acquired data alone, it is possible to generate data on road sites and road framework, at a scale of 1/500. Specific location of road markings and road appurtenances, such as lightings, sound insulation walls, guardrails, manholes, utility poles, road information management facilities etc. can be obtained through direct assessment of the environment and acquired image via MMS. These information can be used as a road database, and plays a crucial role in the establishment of comprehensive maintenance and management system for road infrastructure. (a) Overlaying of acquired feature data both on 3D view and 2D view (b) cross section data overlayed on 3D view and 2D View Figure 5: View of the PADMS interface with acquired topographic features overlay ;(a) Road paint data, (b) road cross section data Road Condition laser surveying Built in the latest version of the PADMS software is the ability to mark and display road surface condition. While rutting (wheel track), longitudinal roughness or evenness can be automatically extracted, to some extent, through 3D point cloud data analysis, it is difficult to acquire road cracks in point cloud data. By taking advantage of the series of high resolution images that MMS captures, highly qualified operators can extract, visually, the road surface condition. Once the road surface have been marked and inspected, the program automatically computes the International Rutting Index(IRI) and generates detailed report of the surface condition. IRI of each segment or section is calculated using the formula IRI 1.33σ+0.24.

5 Figure 6: A section of the road with grid marks identifying portions of roads with defined cracks. Figure 7: Detailed rutting report and results of automatic computation.

6 Figure 8: IRI data results and output. 4. APPLICATIONS 4.1. Public Sector Utilizing MMS systems in the creation and maintenance of Road Management Systems, it is possible to achieve the following; Efficient monitoring of wide variety of information is possible, such as; position coordinates of road appurtenances and other road assets, road surface texture and condition, road facilities and road images. Creation of Road inventory systems for effective management and maintenance of national roads. Collection of basic data aimed at the establishment of Road Asset Management System. Existing Road Information/ Ledger data can be accurately and efficiently updated. Existing management systems that utilizes GIS can be enhanced and supported by accurate road and road facility spatial information Private Sector By taking advantages of the most advanced sensing technologies, MMS provides results in the form of highly precise spatial information, high quality acquisition of images of wide roads, and precise and high resolution 3D coordinate information for road surfaces and road facilites. Automobile manufactures can make use of highly detailed 3D information of roads in driving simulation programs. Car navigation systems manufacturers can utilize the information to create content that make use of advance location information Research Institutions Research facilities can have access to a variety of advanced sensing technologies for road infrastructure data acquisition for use in simulations that accurately mimics the actual condition onsite. 5. CONCLUSION With the current technological advances in the field of remote sensing, and as GPS navigation systems become more widespread and popular, the relative cost of MMS implementations, which primarily utilizes these technologies, has significantly dropped. High flexibility in data acquisition, more information with less time and effort, and high productivity, makes MMS suitable and practical alternative to manual surveying methods employed in current Road Management and Maintenance Systems/Implementations. The utilization of MMS in road surface condition surveying reduces exclusive road use time in site survey operations. Additionally, 3D data of the survey area can be acquired in an efficient yet low cost manner. Through the use of this technology, detailed assessment of the current

7 road condition can be acquired, accurate road database information can be gathered, and an efficient and practical road maintenance system can be implemented. REFERENCES Hein, G.W., Precise Kinematic GPS/INS Positioning: A discussion on the Applications in Aerophotogrammetry, 42nd Photogrammetric Week. Stuttgart, Germany. pp Krabill, W.B., GPS Applications to Laser Profiling and Laser Scanning for Digital terrain Models, 42nd Photogrammetric Week. Stuttgart, Germany. pp Kridakorn, Saksiri, M.L., D Imagery System for Street Mapping In: Asia Geospatial Forum, September 2012, Hanoi, Vietnam Schwarz, K.P., H.E. Martell, N. El-Sheimy, R.Li, M.A. Chapman, and D. Cosandier, 1993a. VISAT - A Mobile Highway Survey System of High Accuracy, Proceedings of the IEEE Vehicle Navigation And Information Systems Conference, October, Ottawa, pp Mitsubishi Mobile Mapping Systems - Mitsubishi Electric website : PASCO Corporation WebSite :